CN105189763B

CN105189763B - Production of methane

Info

Publication number: CN105189763B
Application number: CN201380045544.3A
Authority: CN
Inventors: 史蒂文·艾伦·沃尔福威茨
Original assignee: FFGF Ltd
Current assignee: FFGF Ltd
Priority date: 2012-07-27
Filing date: 2013-07-29
Publication date: 2021-06-18
Anticipated expiration: 2033-07-29
Also published as: CA2880127A1; US20150176030A1; JP2015530873A; MX2015001180A; KR20150064018A; EP2877587B1; RU2620063C2; AU2013294553A1; CA2880127C; BR112015001790A2; BR112015001790B1; JP6190456B2; EP2877587A2; WO2014016815A3; CN105189763A; HUE035671T2; DK2877587T3; ES2651112T3; KR101944026B1; NO2877587T3

Abstract

The present invention relates to a process for producing hydrocarbons from carbon dioxide and water in the presence of hydrogen and methanogen/s. The methanogen/s is/are provided in an aqueous growth substrate that is pressurized with a pressurized fluid comprising carbon dioxide to a pressure of 5 bar to 1000 bar. In one embodiment of the invention, a cathode is provided to generate hydrogen and also to control the pH of the aqueous growth substrate. The invention also relates to a device for carrying out the method.

Description

Production of methane

Background

The planet earth is currently plagued by two major problems that have a serious impact on its inhabitants, namely:

global warming caused by excessive carbon dioxide production; and

excessively high crude oil prices and therefore high gasoline and diesel prices.

It is an object of the present invention to alleviate these problems.

The increased production of engines using fossil fuels leads to an excessive demand for crude oil, which in turn leads to an excessive price. Consumption of these fuels and oil, gas and coal fired power stations, etc. increases the amount of carbon dioxide produced, which leads to global warming. The absorption of carbon dioxide by the trees and the resulting release of oxygen is reduced by the removal of large amounts of forest. This imbalance has been and continues to cumulatively upset the world's ecology.

Efforts to increase engine efficiency and reduce fossil fuel product consumption have little potential for improving the situation due to the exponentially growing population and their expectations. Other techniques are actively being sought.

The means for solving the above problems include:

reducing carbon dioxide in the atmosphere;

reduction of "carbon footprint" (use of carbon products); and

the demand for crude oil and other fossil fuels is reduced (by finding alternatives, resulting in their price being reduced).

It is an object of the present invention to provide a method and apparatus that facilitates the above reduction and further provides for methane production.

Disclosure of Invention

The present invention relates to a process for the production of methane from carbon dioxide, hydrogen and one or more anaerobic archaea methanogens provided in an aqueous growth substrate, which is pressurised to a pressure of from 5 to 1000 bar, typically from 5 to 500 bar, preferably from 5 to 200 bar, more preferably from 10 to 150 bar, more preferably from 20 to 150 bar, most preferably from 40 to 150 bar, using a pressurised fluid consisting of carbon dioxide, or a pressurised fluid consisting of a mixture of carbon dioxide and hydrogen.

Preferably, the process is carried out in a reaction vessel in which sufficient aqueous growth substrate is provided to provide a volume ratio of aqueous growth substrate to headspace of from 1: 1 to 4: 1, typically from 2: 1 to 3: 1.

The aqueous growth substrate may be pressurized with a mixture of hydrogen and carbon dioxide, which may be present in the following molar ratios: 4: 1 to 1: 4, 2: 1 to 1: 4, greater than 1: 1 to 1: 4, or even 1: 2 to 1: 4.

The pH of the aqueous growth medium is preferably maintained in the range of 6 to 7.5, preferably 6.5 to 7.

The methanogen(s) may be hyperthermophilic ultramicro-extremophiles or psychrophiles/psychrophiles and/or extracellular electrogenic (exoelectrogenic) microbial organisms.

The process is carried out at a temperature that is optimal or near optimal for the growth of the methanogen or methanogens.

In the case where the methanogen or methanogens are hyperthermophilic, hyperpolarized anaerobic archaea, the reaction vessel may be operated at a temperature of from 50 ℃ to 400 ℃, preferably from 80 ℃ to 200 ℃, more preferably from 80 ℃ to 150 ℃.

In the case where the methanogen or methanogens are psychrophilic/psychrophilic anaerobic archaea, the reaction vessel may be operated at a temperature of from-50 ℃ to 50 ℃, preferably from-5 ℃ to-20 ℃, most preferably about-15 ℃.

Preferably, the pH of the aqueous growth medium is controlled.

The pH of the aqueous growth medium may be controlled by providing a cathode in the reaction vessel and passing an electric current through the aqueous growth medium to generate hydrogen gas and also controlling the pH using electrolysis.

According to a preferred embodiment of the present invention, there is provided a process for the production of methane from carbon dioxide, hydrogen and one or more anaerobic archaea methanogens, the process comprising the steps of:

a) providing an anode reaction vessel (14) containing a positive electrode (anode) and a liquid electrolytic medium comprising water and an ionizable material;

b) providing a cathode reaction vessel (12) containing a negative electrode (cathode), an electrolytic aqueous growth substrate, methanogen(s), carbon dioxide and hydrogen, wherein the cathode vessel (12) and aqueous growth substrate are pressurized to a pressure of 5 to 1000 bar;

c) connecting a first reaction vessel and a second reaction vessel in a connection that allows electrons and/or ions to pass between the electrolytic media of the anode reaction vessel and the cathode reaction vessel;

d) applying a direct current to the positive electrode and the negative electrode to:

influencing hydrogen ionization in the cathode reaction vessel (12) to produce hydrogen gas and also to increase the pH of the electrolytic aqueous growth substrate; and

-influencing the ionized oxygen in the first reaction vessel (14) to form oxygen gas.

Electrolysis may be performed intermittently to control the pH in the cathode reaction vessel (12).

Methane is recovered from the cathode reaction vessel (12).

Oxygen is recovered from the first reaction vessel (14).

The reaction vessels (12) and (14) operate at the same internal pressure and may operate at different temperatures.

The means of attachment is preferably an electrolytic medium, in which case a membrane is provided which allows the passage of electrons and possibly some ions.

Preferably, the connection means has a valve insulated from the electrolyte.

The reactor vessel may be operated under different conditions, for example the anode reactor vessel (14) may be operated at ambient temperature of about 25 ℃ and the cathode reactor vessel (12) may be operated at a temperature that is optimal or near optimal for the growth of the methanogen or methanogens.

In the case where the methanogen or methanogens are hyperthermophilic, hyperpolarized anaerobic archaea, the cathode reaction vessel (12) may be operated at a temperature of from 50 ℃ to 400 ℃, preferably from 80 ℃ to 200 ℃, more preferably from 80 ℃ to 150 ℃.

In the case where the methanogen or methanogens are psychrophilic/psychrophilic anaerobic archaea, the cathode reaction vessel (12) may be operated at a temperature of from-50 ℃ to 50 ℃, preferably from-5 ℃ to-20 ℃, most preferably about-15 ℃.

The cathode reaction vessel (12) and the anode reaction vessel (14) may be pressurised with a pressurised fluid consisting of a mixture of carbon dioxide and hydrogen to a pressure of from 5 to 500 bar, preferably from 5 to 200 bar, more preferably from 10 to 150 bar, more preferably from 20 to 150 bar, most preferably from 40 to 150 bar.

The cathode reaction vessel (12) may be pressurized with a mixture of hydrogen and carbon dioxide, which may be present in the following molar ratios: 4: 1 to 1: 4, 2: 1 to 1: 4, greater than 1: 1 to 1: 4, or even 1: 2 to 1: 4.

Preferably, sufficient aqueous growth substrate is provided in the cathode reaction vessel (12) to provide a volume ratio of aqueous growth substrate to headspace of from 1: 1 to 4: 1, typically from 2: 1 to 3: 1.

The voltage applied across the positive and negative electrodes may be-0.2 v to-40 v, -2v to-40 v, -10v to-40 v, -20v to-40 v, typically-25 v to-35 v.

The direct current flowing across the positive and negative electrodes may be about 75 to 125 milliamperes.

According to a second embodiment of the present invention, there is provided an apparatus for producing methane from carbon dioxide, hydrogen and one or more anaerobic archaea methanogens, the apparatus comprising:

a cathode reaction vessel (12) for containing carbon dioxide and electrolyzed water;

an anode reaction vessel (14) for containing electrolyzed water;

a negative electrode (cathode) which is positioned in the cathode reaction container (12) and can support anaerobic archaea methanogen;

a positive electrode (anode) positioned within the anode reaction vessel (14); and

connecting means for connecting the electrolyzed water in the cathode reaction vessel (12) and the anode reaction vessel (14) so that an electric current can flow therebetween,

characterized in that the cathode reaction vessel (12) and the anode reaction vessel (14) are adapted to be pressurized to a pressure of 5 to 1000 bar, the cathode reaction vessel (12) is adapted to be pressurized with a pressurized fluid consisting of carbon dioxide, or a mixture of carbon dioxide and hydrogen, and the inner surfaces of the cathode reaction vessel (12) and the anode reaction vessel (14) are made of a non-conductive, non-corrosive material which insulates the electrolytic medium from the rest of the apparatus, except for the cathode and anode which are in contact with the electrolytic water inside the reaction vessels.

Preferably, the cathode reaction vessel (12) and the anode reaction vessel (14) are adapted to be pressurised to a pressure of from 5 to 500 bar, preferably from 5 to 200 bar, more preferably from 10 to 150 bar, more preferably from 20 to 150 bar, most preferably from 40 to 150 bar.

Preferably, the connection means is a conduit containing a liquid electrolyte.

The conduit may include a semi-permeable membrane that allows ions to pass between the electrolyzed water in the anode reaction vessel (14) and the cathode reaction vessel (12).

Preferably, the conduit has a valve that is not in electrical contact with the electrolyte.

Preferably, the negative electrodes in the cathode reaction vessel (12) are in the form of a porous structure capable of supporting methanogens and their producible biofilms. For example, the cathode in the second reaction vessel (12) is a hollow microporous cylinder which is closed at one end and made of Pt amalgam or Pt, or a platinum group metal, or titanium plated with a platinum group metal.

Preferably, the positive electrode of the anode reaction vessel (14) is made of Pt or a platinum group metal, or electroplated titanium.

Preferably, the apparatus includes means for equalizing the pressure in the cathode reaction vessel (12) and the anode reaction vessel (14).

Preferably, the pressure equalisation means is pressurised by the pressurised fluid used to pressurise the cathode reaction vessel (14) and also simultaneously pressurise the anode reaction vessel (12).

Preferably, the pressure equalization means provides electrical insulation between the cathode reaction vessel (12) and the anode reaction vessel (14).

The pressure equalizing device may include a non-conductive, high tensile, high temperature resistant tube having a piston located therein, and an indicator for indicating the position of the piston within the tube.

Preferably, the apparatus includes thermal control means for heating or cooling the cathode reaction vessel (12).

Preferably, an agitator is provided within the cathode reaction vessel (12).

The conduit may be located in a non-conductive heat resistant barrier between the cathode reaction vessel (12) and the anode reaction vessel (14).

Drawings

FIG. 1 is a side view of a reactor according to one embodiment of the present invention;

FIG. 2 is a cross-sectional view of the reactor shown in FIG. 1 taken along line 2-2;

FIG. 3 is a cross-sectional view of an apparatus for equalizing pressure within a reaction vessel on a reactor according to one embodiment of the present invention;

FIG. 4 is a graph showing CO measurement₂Graph of experimental results on the effect of pH on an electrolytic aqueous growth substrate.

FIG. 5 is a graph showing the results of an experiment for measuring the influence of electrolysis on the pH of the electrolytic medium used in the present invention.

Fig. 6 is a graph showing the results of an experiment using thermoautotrophic methanococcus thermophilus (mc. thermolithrotropicus), 5 bar, 30V, 65 ℃;

FIG. 7 is a graph showing the results of an experiment using thermoautotrophic methanococcus thermophilus, 5 bar, 12V, 65 ℃;

FIG. 8 is a graph showing the results of an experiment using Thermoautotrophic Methanococcus methanolica, 10 bar, 30V, 65 ℃;

FIG. 9 is a graph showing the results of an experiment using Thermoautotrophic Methanococcus methanolica, 20 bar, 30V, 65 ℃;

fig. 10 is a graph showing the results of an experiment showing that oxygen is generated in the anode reaction vessel of the present invention.

FIG. 11 is a graph showing the results of an experiment using Methanopyrus kandeli (M.kandleri), 10 bar, 30V, 97 ℃;

FIG. 12 is a graph showing the results of an experiment using Methanopyrus kanehensis, 20 bar, 30V, 97 ℃;

FIG. 13 is a graph showing the results of an experiment using Methanopyrus kanehensis, 20 bar, 30V, 105 ℃;

fig. 14 is a graph showing the results of an experiment using s.jannaschii (mc. jannaschii), 10 bar, 30V, 85 ℃;

FIG. 15 is a graph showing the results of an experiment using S.jannaschii, 10 bar, 30V, 92 ℃;

FIG. 16 is a graph showing the results of an experiment using S.jannaschii, 20 bar, 30V, 92 ℃; and

FIG. 17 is a graph showing the results of an experiment using S.jannaschii, 30 bar, 92 ℃.

Detailed Description

The present invention relates to a process for the production of methane from methanogenic archaea (methanogens) cultured in an aqueous matrix solution, using a pressurized fluid comprising carbon dioxide, at a high pressure of greater than or equal to 5 bar and up to 1000 bar, in the presence of carbon dioxide and hydrogen. The invention also relates to a device for carrying out a methanogenic reaction.

The methanogenic reaction is maintained under anaerobic conditions.

Referring to fig. 1 and 2, methanogens are cultured in a reactor, generally indicated by the numeral 10. The reactor 10 comprises

reaction chambers

12 and 14, which are suitable for operating at temperatures up to 500 ℃ or greater than or equal to 500 ℃ and internal pressures greater than or equal to 5 bar and up to 1000 bar.

The

reaction chambers

12 and 14 are defined in a tube 16 of a non-conductive material capable of withstanding high temperatures, in this case Polyetheretherketone (PEEK), the tube 16 being reinforced within a metal housing 18 held together by metal tie rods 19.

A positive electrode (anode) 20 made of sintered platinum or rhodium-plated titanium extends into the "anode" reaction chamber 14. An outlet 22 is provided to remove material from the anode reaction chamber 14 and

inlets

24 and 26 are provided to supply material into the anode reaction chamber 14.

A negative electrode (cathode) 28 made of sintered platinum or rhodium-plated titanium or titanium extends into the "cathode" reaction chamber 12. The negative electrode 28 has a hollow core 30 and a perforated disc 32 coated with a carbon cloth 34 and which facilitates the formation of a biofilm by methanogens, which carbon cloth 34 is capable of supporting methanogens.

An insulating barrier 36 made of a non-conductive material, preferably PEEK, separates the

reaction chambers

12 and 14, the

reaction chambers

12 and 14 being connected by a conduit 38 extending through the barrier 36. The conduit 38 includes a valve mechanism for opening and closing the conduit 38. The valve is insulated from the contents of the

reaction chambers

12 and 14 and contains a threaded segmented smooth rod which when screwed in allows the smooth rod segment to pass through a "dog-leg" in the conduit to effectively block electrolyte continuity when fully screwed in. The membrane is secured within a hollow vessel within the conduit 38. The cavity reservoir is located within the conduit 38 separating the anode side of the valves of the two

reservoirs

12 and 14 to accommodate a pair of short apertures/sleeves to secure the membrane therebetween. The hole/sleeve is located and secured in position within the container by a non-conductive circlip.

The distance between the

electrodes

20 and 28 is preferably 60mm or less. The interior surfaces of the

reaction chambers

12 and 14, including the valve electrolyte contact surfaces, insulate the electrolytic medium within these chambers from the rest of the apparatus, except for the

electrodes

20 and 28 which are in contact with the electrolytic medium within the

chambers

12 and 14.

A non-conductive coated magnetic stir bar 40 is located within the cathode reaction chamber 12 below the carbon cloth 34 and is driven by a rotating magnetic stirring mechanism 42.

An outlet 44 is provided to remove material from the cathode reaction chamber 12 and

inlets

46, 48 and 50 are provided to supply material into the cathode reaction chamber 12.

The outlet may have an electrically, pneumatically or hydraulically operated solenoid valve (not shown in the drawings) which connects the reactor with the outlet connection to an external collection or supply vessel.

The

electrodes

20 and 28 are connected together and powered by a dc power supply.

Means are provided to control the pressure within the anode reaction vessel 14 and balance its internal pressure with the pressure within the cathode reaction vessel 12: referring to FIG. 3, pressurized CO₂And/or H₂/CO₂The mixture 60 is supplied directly to the inlet 50 of the cathode reaction vessel. Pressurized CO₂And/or H₂/CO₂Connected to the anode reaction vessel via a high pressure balancer 62, said high pressure balancer 62 blocking the pressurized CO₂And/or H₂/CO₂The mixture contacts or reacts with the contents of the anode reaction vessel 14. The high pressure balancer 62 comprises a tube 64 made of non-conductive, high tensile, high temperature resistant tubing and is covered by a housing 66 capable of withstanding high pressures above 5 bar but up to 1000 bar. A piston 68 is located within the conduit 64. The piston 68 is movable along the length of the conduit 66And sealing the CO on the cathode side of conduit 66 to the electrolyte on the anode side of conduit 64₂And/or H₂/CO₂The mixture while equally transmitting pressure to the anode contents. An indicator is provided to indicate the position of the piston 68 within the tube 64-in this case a magnetic metal ball 70 located within the piston 68, the magnetic metal ball 70 activating a light emitting diode (LED, not shown) located along the length of the tube 64. The LED lights up when in contact with the magnetic field of the magnetic ball 70, indicating the position of the piston 68 within the tube 64.

In use, prior to the start of the electrolysis process, the valve in conduit 38 is closed and anolyte is transferred to the anode reaction vessel 14 through inlet 26. The anolyte comprises a solution containing 1.25M Mg₂SO₄An aqueous solution of (a).

The aqueous methanogen substrate solution is transferred to the cathode reaction vessel 12 through inlet 48. The aqueous base solution comprises a combination of: minerals (mainly chloride, sulphate and carbonate, and wolff (Wolfe) minerals) and methanogenic vitamins, such as the methane-producing bacteria-capable vitamin. The pH of the solution is in the range of 6 to 7.5, preferably 6.5 to 7. The solution is inoculated with one or more methanogen cells under anaerobic conditions and then transferred to the cathode reaction vessel through inlet 46. Sufficient aqueous methanogen substrate solution is transferred to the cathode reaction vessel 12 to leave an anaerobic headspace. The ratio between the volume of the headspace and the volume of the solution is generally from 1: 1 to 1: 3.

The inlet 26 of the anode reaction vessel 14 is connected to a pressure balancer 62. CO 2₂Is pumped into the cathode reaction vessel 12 through inlet 48 to purge the headspace of air, including oxygen, which exits through outlet 44. Closing

inlets

24, 48 and 46 and

outlets

22 and 24 and using liquid CO₂The cathode reaction vessel 12 is pressurized. When the pressure in the

reaction vessels

12 and 14 is the same, the valve in conduit 38 is opened and the same pressure is maintained in the

reaction vessels

12 and 14 using the high pressure balancer 62. The pressure in the

reaction vessels

12 and 14 may be maintained at 5 bar to 1000 bar. It has been found that CO is increased₂Can lead to an aqueous methanogen substrateThe pH of the solution decreases. This is problematic when the pH reaches below 5.5. Ideally, the pH needs to be maintained in the range of 6 to 7.5, preferably 6.5 to 7.

The temperatures within the

reaction vessels

12 and 14 may be the same, or they may be heated or cooled separately by heating or cooling the circulating material of the vessels. The temperature within the reaction vessel 12 may be controlled by heating the insulated copper or thermally conductive material 51 with a heating cartridge or one or more heating elements adjacent the insulated copper or thermally conductive material 51.

The one or more methanogens may be anaerobic archaea, which may be hyperthermophilic, hyperthermophilic or psychrophilic/psychrophilic and/or extracellular electrogenic microbial organisms.

Examples of methanogens include Methanobacterium alcaliphilum (Methanobacterium alcaliphilum), Methanobacterium buchneri (Methanobacterium bryantii), Methanobacterium congolense (Methanobacterium congolense), Methanobacterium delbrueckii (Methanobacterium defluvivii), Methanobacterium ehrenbergii (Methanobacterium esplanae), Methanobacterium formicum formate (Methanobacterium formicum), Methanobacterium evans (Methanobacterium ivanovvii), Methanobacterium palusteri (Methanobacterium palustrum), Methanobacterium thermonatum (Methanobacterium thermonatum), Methanobacterium pusillus (Methanobacterium thermonatum), Methanobacterium acidiprodicum (Methanobacterium acidiprodii), Methanobacterium fumonis (Methanobacterium acidi), Methanobacterium fumus (Methanobacterium acidilans), Methanobacterium fumonis (Methanobacterium acidilabacterium acidilactinatum), Methanobacterium fumonis (Methanobacterium acidilactinatum), Methanobacterium fumonis, Methanobacterium acidiprodii (Methanobacterium), Methanobacterium aureobacterium acidilaginosum), Methanobacterium acidilactinatum, Methanobacterium acidi (Methanobacterium acidilagineum), Methanobacterium acidi, Methanobacterium acidilabacterium acidilagineum, Methanobacterium acidila, Methanobacterium acidilagineum, Methanobacterium, Thermoautotrophic methanothermophilus (Methanobacterium thermoautotrophicum), Methanobacterium thermoautotrophicum (Methanobacterium thermoautotrophicum), Methanobacterium flexneri (Methanobacterium thermoflexneri), Methanobacterium thermonathigera (Methanobacterium thermonatriensis), Methanobacterium thermonathigera (Methanobacterium thermonathigeras), Methanobacterium Vol.vonius (Methanobacterium thermonathigera), Methanobacterium thermonatriens (Methanobacterium occium), Methanobacterium thermonatum bravaicum (Methanobacterium thermonathicalis), Methanobacterium acidium morum (Methanobacterium paravum), Methanobacterium thermonatum portuginosus (Methanobacterium thermonatriensis), Methanobacterium thermonatriensis (Methanobacterium thermonatriensis), Methanobacterium thermonatriensis, Methanobacterium thermonat, Methanococcus maripalustris (Methanococcus maripaludis), Methanococcus vannielii (Methanococcus vannielii), Methanococcus wovensis (Methanococcus voltaea), Methanococcus thermoautotrophic Methanococcus thermophilus (Methanococcus thermolithrotropicus).

In the case where the methanogen or methanogens are hyperthermophilic, hyperpolarized anaerobic archaea, the cathode reaction vessel (12) may be operated at a temperature of from 50 ℃ to 400 ℃, preferably from 80 ℃ to 200 ℃, more preferably from 80 ℃ to 150 ℃. In the case where the methanogen or methanogens are psychrophilic/psychrophilic anaerobic archaea, the cathode reaction vessel (12) may be operated at a temperature of from-50 ℃ to 50 ℃, preferably from-5 ℃ to-20 ℃, most preferably about-15 ℃.

In addition to CO₂In addition, H may be introduced through inlet 50₂Are respectively supplied to the cathode reaction vessel 12 to make the cathode reaction vessel CO₂/H₂The mixture of (a) is pressurized. H may be added in a molar ratio of 4: 1 to 1: 4, 2: 1 to 1: 4, 1: 1 to 1: 4, or even 1: 2 to 1: 4₂And CO₂。CO₂And H₂Is maximized by excluding other substances for pressurization so that the maximum reaction system volume can be used for CH₄The transformation of (3).

Typical methanogens according to the present invention are thermophilic methanogenic archaea, such as: the preferred temperature of the Methanococcus (Methanococcus) class, i.e., Methanococcus jannaschii (formerly Methanococcus jannaschii), is 85 ℃, and the preferred temperature of the Methanopyrus genus, i.e., Methanopyrus kandeli (Methanopyrus kandeli), is 105 ℃, and the preferred temperature of the Methanopyrus thermophilus genus, i.e., Methanopyrus thermoautotrophicus (Methanococcus thermoautotrophicus) is 65 ℃.

The electrolytic reaction is initiated by applying a direct voltage of-0.2 v up to-35 v, typically-20 v to-35 v, across the positive electrode 20 and the negative electrode 28. The direct current flowing across the positive and negative electrodes may be about 75 to 125 milliamps, typically about 100 milliamps. The applied charge ionizes atoms in the electrolytic medium within the reaction vessel. Initiation of the electrolysis process results from H present in the electrolysis medium₂O forms nascent (ionized) hydrogen ions. According to the invention, the electrolysis process not only produces hydrogen but also raises the pH of the aqueous substrate solution, and the pH of the solution can be controlled to a pH above 5.5 at which methanogens can not only produce methane, but can also grow (i.e. multiply) in the range of 6 to 7.5, preferably 6.5 to 7. According to one method according to the invention, the pH of the initial aqueous matrix solution is provided in the correct range of 6 to 7.5 by the electrolyte in the medium. With CO₂Pressurization increases the acidity and thereby lowers the pH. If the pH drops too low, electrolysis is performed intermittently to increase the alkalinity and raise the pH to the desired range.

Reaction products, including hydrocarbons, may be taken from outlet 44. In the anode reaction vessel 14, the flow of electrons causes negatively charged oxygen ions to be attracted to the positively charged electrode 20 therein, thereby releasing oxygen molecules at the electrode. Oxygen product may be taken from outlet 22.

A conduit 38, which may have cation one-way flow properties, is necessary to allow electron transfer and to isolate oxygen released in the reaction vessel 14 from the reaction vessel 12, thereby avoiding recombination with carbon and/or hydrogen therein and oxygen contamination of anaerobic archaea. The barrier 36 also serves to reduce heat transfer so that different temperature conditions can be maintained in the

reaction vessels

12 and 14, thereby enhancing and facilitating the different reactions occurring therein and saving energy costs.

If necessary, methanogens can be supplied to the reaction chamber 12 through the hollow core 30 of the electrode 28 and stay on the carbon cloth 34, which carbon cloth 34 provides a shelter for the methanogens to produce biofilm and methanogenesis.

Charge polarization is used to separate the produced methane and oxygen from each other for a sufficiently short time for the methanogens to perform their conversion work and also to enhance the process by enhanced electrolysis. During this process oxygen is generated at the anode 20 remote from the negatively charged cathode 28, where the methanogenic reaction takes place, providing sufficiently anaerobic conditions in the vicinity of the cathode while current flows through the circuit.

The output stream can be recycled after separation of the produced methane and unreacted materials, enabling removal of dead or inactive methanogens, and the process can be repeated continuously.

In accordance with another aspect of the present invention, it has been found that by adding hydrogen to the headspace of the cathode reaction vessel 14, the methanogenic reaction can be enhanced at higher pressures.

According to one embodiment of the invention, standard procedures are established and the standard conditions are:

cathode: 100ml headspace, 300ml medium; seeding with 0.5g of frozen cells

Anode: with 1.25M MgSO₄The solution (. about.100 ml) was completely filled

Voltage: 30V

The process comprises the following steps: inoculation was carried out at room temperature and electrolysis was automatically started at night. The first headspace measurement was in the morning of the following day. If the hydrogen content is > 50% by volume, the electrolysis is stopped. Heating to the appropriate temperature is then commenced. Several headspace measurements (inoculation-3 hours, inoculation 6 hours, in the following morning) follow until the hydrogen produced has been (completely) converted to methane.

Three strains of hyperthermophilic methanogens were used: the experiments were carried out using the apparatus shown in FIGS. 1 to 3 and described above for Methanococcus jannaschii (old name Methanococcus jannaschii), Methanopyrus kanehensis-the preferred temperature is 105 deg.C, and Methanococcus thermoautotrophic Methanothermus Methanococcus methanothermus. All three strains have been tested according to this procedure.

The following experiments were performed:

1. thermoautotrophic Methanothermophilus, 10 bar, 30V, 65 ℃, 300ml electrolyte/100 ml headspace

2. Thermoautotrophic Methanothermophilus, 20 bar, 30V, 65 ℃, 300ml electrolyte/100 ml headspace

3. Pyrolusitum kanehelii, 10 bar, 30V, 97 ℃, 300ml electrolyte/100 ml headspace

4. Pyrolusitum kanehelii, 20 bar, 30V, 97 ℃, 300ml electrolyte/100 ml headspace

5. Pyrolusitum kanehelii, 20 bar, 30V, 105 ℃, 300ml electrolyte/100 ml headspace

6. Methanococcus jannaschii, 10 bar, 30V, 85 ℃, 300ml electrolyte/100 ml headspace

7. Methanococcus jannaschii, 10 bar, 30V, 92 ℃, 300ml electrolyte/100 ml headspace

8. Methanococcus jannaschii, 20 bar, 30V, 92 ℃, 300ml electrolyte/100 ml headspace

A summary of the test results is provided in table 1 below:

TABLE 1

The results, as reflected in table 1, indicate that the production rate of methane and the total volume% of methane increase with increasing pressure and test temperature. The cultivation temperature of the individual organisms should be around its optimum temperature.

Reference example 13-experiment with S.jannaschii at 30V, 92 ℃ and 10 bar:

about 57 vol% H was produced by electrolysis at 30V₂(initial headspace)

Methanogens completely convert hydrogen to 19% by volume CH at a constant temperature of 92 deg.C₄。H₂The final volume percentage in the headspace was 1 vol%

H₂To CH₄The conversion of (A) was 98.2%

CH₄The production rate of (A) is 12.1ml/h

Reference example 14-experiment with S.jannaschii at 30V, 92 ℃ and 20 bar:

65.5 vol.% H was produced by electrolysis₂(initial headspace)

Methanogens completely convert hydrogen to 31% by volume CH at a constant temperature of 92 deg.C₄。H₂The final volume percentage in the headspace was 0.4 vol%

H₂To CH₄The conversion of (A) was 99.4%

CH₄The production rate of (A) was 21.1ml/h

The two experiments were comparable as the temperature, electrolyte, ratio of headspace to medium, seeding procedure and voltage were kept constant. No external hydrogen was added.

These two experiments support the following conclusions:

1. increased pressure increases efficiency and is increased by H₂(by H)₂Electrolytic production of O) and CO₂To CH₄The biological production rate of (c). The conversion in the 20 bar experiment was higher than the conversion in the 10 bar experiment.

2. Methanogens use up all of the hydrogen produced due to the production of methane by methanogenesis.

3. Biological production of methane (methanogenesis) using the process of the invention does not necessarily require 4: 1H₂∶CO₂And (4) the ratio. When CO is present₂Complete consumption of hydrogen in excess may be advantageous (in comparison to 4: 1 hydrogen: CO)₂Ratio).

1 atm 101325kPa

1 bar 100kPa

The invention will now be described in more detail with reference to the following non-limiting examples.

Example 1

In this example, three methanogens were tested: methane production by Pyrococcus kanehensis, Thermoautotrophic Methanococcus methanothermus, and Methanococcus jannaschii was tested.

The following growth aqueous matrix solutions (growth media) were used in this example:

MJ Medium-for Methanococcus jannaschii

SME Medium-Methylobacillus kanehensis

MGG Medium-for thermoautotrophic methanothermophilus

Example 2CO at 50 bar₂Experiment, not electrolyzing

This experiment was performed to determine CO₂Influence on the pH of the electrolyte.

At 65 ℃ with 50 bar CO₂The test was started. The electrolyte in the cathode compartment was SME, pH 7. The change in pH was monitored every 15 minutes. The results of the experiment are shown in table 2 below.

TABLE 2

Date	Time	Pressure of	Temperature of	Cathode pH
					5.12.12	11.00	Atmosphere (es)	65℃	7
5.12.12	13.50	50 bar CO₂	65℃	7
					5.12.12	14.05	50 bar CO₂	65℃	6.5
5.12.12	14.20	50 bar CO₂	65℃	5.5
					5.12.12	14.35	50 bar CO₂	65℃	5.5
5.12.12	14.50	50 bar CO₂	65℃	5.5
					5.12.12	14.02	80 bar CO₂	65℃	Pressurizing to 80 bar
5.12.12	14.17	80 bar CO₂	65℃	5.5

CO₂The effect on pH is shown in figure 4.

And (4) conclusion: at 50 bar CO₂From 7 to 5.5 and remains constant at this value. A pH of 5.5 is the minimum pH that methanogens can tolerate.

Example 2At 65 ℃ and atmospheric pressure (absence of CO)₂) Electrolytic experiment of

This experiment was performed to determine when CO was present₂The effect of the electrolysis reaction on the pH in the absence of the catalyst.

Electrolyte: SME (cathode), chloride-free SME (anode)

Voltage: 31.5V constant

Gas phase: air (a)

The results of the experiment are shown in table 3 and fig. 5.

TABLE 3

	Start (65 ℃ C.)	After 15 minutes	After 30 minutes	After 45 minutes	After 1 hour	After 2 hours
							Electric current	220mA	250mA	320mA	300mA	320mA	300mA
Anodic pH	6.5	5.5	3.5	2.5	2	2
							Cathode pH	8	9	10	11	11	11

The pH at the cathode increased from 8 to 11, remaining constant at 11. The pH at the anode became acidic, decreasing from 6.5 to 2.

And (4) conclusion: due to electrolysis, the electrolyte in the cathode becomes alkaline and the anode reaction chamber becomes acidic. The pH 11 at the cathode is too high for methanogens. Their pH ranges from 5.5 to 8, most preferably around 7. The electrolysis reaction can be used to control the pH of the solution.

Example 4

CO at 5 bar₂And FFGF reaction at 30V using thermoautotrophic Methanococcus methanothermophilus

Cathode electrolyte: 280ml SME, pH 6.5

Anode electrolyte: mg (magnesium)₂SO₄，1.25M

Inoculation: 0.8g of frozen cells and 20ml of preculture liquid

Gas phase: 5 bar CO₂

Electrolysis was started immediately after inoculation; heating to final temperature when sufficient hydrogen is present

Voltage: 30V

The results of the experiment are shown in FIG. 6.

In this experiment only CO was present in the headspace₂Without additional hydrogen. Hydrogen is generated only by electrolysis, which is carried out immediately after inoculationThe moment begins. Heat was switched to activate methanogens at a hydrogen concentration of 45%. The electrolysis was continued for another 3.5 hours until it was stopped. Methanogens produced by CO at night₂And hydrogen to 15% methane. The final measurement showed that the headspace contained 25% methane. After the experiment it was noted that the frozen cells were located on top of the cathode without resuspension in the medium. Therefore, liquid preculture was performed in the following experiment.

Example 5

CO at 5 bar₂And FFGF reaction at 12V using thermoautotrophic Methanococcus methanothermophilus

Cathode electrolyte: 240ml of SME, pH 6.5

Anode electrolyte: mg (magnesium)₂SO₄，1.25M

Inoculation: 60ml of preculture liquid

Gas phase: 5 bar CO₂

Voltage: 12V

Discard 5ml of gas sample and analyze 10ml of gas sample

The results of this experiment are shown in figure 7.

Under the same conditions as example 4 but at 12V electrolysis it took longer to produce similar amount of hydrogen from electrolysis (8 hours and > 33% H)₂Compared to 2.5 hours and 45% H₂). The electrolysis was stopped at night. In the morning, methanogens have already mixed hydrogen and CO₂Conversion to 6% methane. Electrolysis was restarted to investigate if more methane was produced and the situation was: up to 8% CH₄To the final concentration of (c). This yield is two thirds less when compared to the 5 bar experiment described in example 4 at 30V. The conclusion is that more methane can be produced at higher voltages.

Example 6

CO at 10 bar₂And FFGF reaction at 30V using thermoautotrophic Methanococcus methanothermophilus

Cathode electrolyte: 240ml of SME, pH 7

Anode electrolyte: mg (magnesium)₂SO₄，1.25M

Inoculation: 60ml of preculture liquid

Gas phase: 10 bar CO₂

Voltage: 30V

The results of this experiment are shown in fig. 8.

CO at 10 bar for this experiment₂Without additional hydrogen. Hydrogen gas was generated by electrolysis at 30V, which was automatically started at midnight. At this stage the reactor was at room temperature. In the morning, 70% H was detected in the gas phase when electrolysis was carried out for 8.5 hours₂. The reactor was heated to bring the methanogens into an active mode (see figure 8). Electrolysis was started for 3.5 hours. The next day we were able to detect a final concentration of methane of 18%.

Example 7

CO at 20 bar₂And FFGF reaction at 30V using thermoautotrophic Methanococcus methanothermophilus

Cathode electrolyte: 240ml of SME, pH 7

Anode electrolyte: mg (magnesium)₂SO₄，1.25M

Inoculation: 60ml of preculture liquid

Gas phase: 20 bar CO₂

The timing switch controls the electrolysis to automatically start at 22:00

Voltage: 30V

The results of this experiment are shown in fig. 9.

CO at 20 bar for this experiment₂Without additional hydrogen. Hydrogen was produced by electrolysis at 30V, automatically started at 22:00 nighttime. At this stage the reactor was at room temperature. In the morning, 63% H was detected in the gas phase when electrolysis was carried out for 10.25 hours₂. Switch to heat to activate methanogens (see figure 9). The final methane concentration was-22.5%.

Example 8

The gas at the anode was sampled and analyzed in GC. Oxygen can be detected (but not quantitatively; nitrogen as a carrier gas is not suitable for oxygen) with our GC machineGas quantification). However, two criteria (100% pure oxygen and air about 21% O) were used for a rough estimate of the amount of oxygen produced at the anode₂) Make a "calibration curve". The resulting peaks (at the same retention time) have different areas. By plotting the area (which is proportional to the amount of gas injected) against the volume percentage, a "calibration curve" was obtained (see fig. 10). After injecting the "anode" sample of unknown composition we can roughly estimate the volume percentage of oxygen, corresponding to-30% (note that electrolysis was performed at 30V for-13 hours in this case). Although the calibration curve for only two measurement points under given conditions (nitrogen as carrier gas) is not accurate for accurate quantification, it can be said that the amount of oxygen in the anode is higher than in air. It was thus demonstrated that oxygen was generated at the anode reactor.

Example 9

CO at 10 bar₂And methane fire Kam (97 ℃) at 30V, seeding the catholyte with frozen cells: 280ml SME, pH 6

Anode electrolyte: mg (magnesium)₂SO₄，1.25M

Inoculation: 0.5g of frozen cells, resuspended in 20ml of SME under anaerobic conditions

Gas phase: 10 bar CO₂

Electrolysis was started at room temperature (30v) at night via timer for 6 hours

Heating was initiated in the morning when sufficient hydrogen was present

A15 ml sample of gas was taken, 5ml (dead volume) was removed, and 10ml was used for analysis of 200. mu.l aliquots

The results of this experiment are shown in fig. 11.

The use of methane-producing fire bacteria of Kam at 10 bar CO₂The experiment did produce methane. The use of frozen cells as inoculum is a successful approach. Electrolysis started at room temperature and-85% hydrogen was generated within 6 hours. The methanogen produced 15% by volume of CH at 97 ℃ in the day of cultivation₄. It was decided to use frozen M.kansei cells for subsequent experiments.

Example 10

CO at 20 bar₂And Methanopyrus kanehensis (97 ℃) at 30V, inoculating with frozen cells

Cathode electrolyte: 280ml SME, pH 6

Anode electrolyte: mg (magnesium)₂SO₄，1.25M

Gas phase: 20 bar CO₂

Electrolysis was started immediately after inoculation (30V)

Heating is initiated when sufficient hydrogen is generated by electrolysis

The results of this experiment are provided in fig. 12.

Here, 20 bar CO is used₂In the experiment of (3), the resuspended frozen cells were seeded and electrolysis was started immediately at room temperature. At night, after 7 hours, the electrolysis was stopped and the reactor was heated (50% H present)₂). Overnight, the methane-producing bacterium Kam general strain H₂And CO₂Conversion to-25% methane. We then resumed electrolysis but the current rapidly dropped to 0.07 to 0.01A. After releasing the gas generated in the anode reaction chamber (> 200ml), the current was increased immediately but only for a short time. Interestingly, H in the cathode headspace after anode gas evolution₂And CO₂The percentage of (c) is also reduced. Because of the low current, no more H can be generated₂. Remaining H₂(evening-6%) was completely converted to methane by active methanogens overnight.

Example 11

CO at 20 bar₂And Methanopyrus kanehensis (105.5 ℃) at 30V, inoculated with frozen cells

Cathode electrolyte: 280ml SME, pH 6

Anode electrolyte: mg (magnesium)₂SO₄，1.25M

Gas phase: 20 bar CO₂

Electrolysis (30V) was started at room temperature at night via timer for 6 hours

In the morning, heating was initiated when sufficient hydrogen was present

The results of this experiment are shown in fig. 13.

In this experiment electrolysis was started at room temperature. Within 8 hours-60% of the hydrogen is produced by electrolysis (20 bar CO initially)₂Below) sufficient to support the growth of methanogens. Heating was started at 10:00 and methanogens immediately started to produce methane, so 2% CH could be detected at night₄(see FIG. 13). Methanogens converted all hydrogen to methane to a final concentration of 19% within 24 hours. If more hydrogen is present, the methanogen will likely produce even more methane.

Example 12

CO at 10 bar ₂30V and 85 ℃ Meanococcus jannaschii

Cathode electrolyte: 240ml of medium, pH 6.5 and 60ml of preculture liquid

Anode electrolyte: mg (magnesium)₂SO₄，1.25M

Initial gas phase: 10 bar CO₂

Electrolysis (30V) was started at room temperature at night via timer for 8 hours

Measuring the hydrogen content in the morning and adding additional hydrogen if necessary, and then starting heating

The results of this experiment are provided in fig. 14.

Inoculation of the preculture liquid and CO at 10 bar₂The following begins. The electrolysis was carried out at 30V for 8 hours. The methane concentration after 22.5 hours of inoculation at the final temperature (85 ℃) was-30% by volume, which corresponds to a total of 244ml methane. The gas is then released and external hydrogen is added.

Example 13

At 10 barCO ₂30V and 92 ℃ C. jannaschii

Cathode electrolyte: 280ml of medium, pH 6.5 and 0.5g of frozen cells, resuspended in 20ml under anaerobic conditions

Anode electrolyte: mg (magnesium)₂SO₄，1.25M

Initial gas phase: 20 bar CO₂

Electrolysis was started at room temperature (30V) via a timer at night,

measuring the hydrogen content in the morning, adding additional hydrogen if necessary, and then starting heating

The results of this experiment are shown in fig. 15.

This test produced a total of 19.5 vol% without the addition of external hydrogen (see figure 15). Methanogens converted all of the hydrogen present to methane within a total incubation time of 41.5 hours.

Example 14

CO at 20 bar ₂30V and 92 ℃ C. jannaschii

Anode electrolyte: mg (magnesium)₂SO₄，1.25M

Initial gas phase: 20 bar CO₂

Electrolysis was started at room temperature (30V) via a timer at night,

The results of this experiment are shown in fig. 16.

This test produced 31 vol% methane, which corresponds to 465ml of gaseous methane (see FIG. 16). No external hydrogen was added. All of the hydrogen present is produced by electrolysis and is utilized by the methanogens to synthesize methane.

Example 15

H at 92 ℃ at 30 bar₂/CO₂Adding external hydrogen into the methane-warming jensenii,

Anode electrolyte: mg (magnesium)₂SO₄，1.25M

Initial gas phase: 15 bar CO₂And 15 bar external hydrogen > 30 bar H₂/CO₂Gas phase, 70/30(v/v) H₂/CO₂

Not electrolyzed

Determination of the time taken to convert all of the hydrogen to methane

Determination of CH₄Production rate of

The results of this experiment are shown in fig. 17.

At 80/20(v/v) H₂/CO₂The experiment was started at the initial ratio (see fig. 17). The methanotropha jensenii required 22.5 hours of incubation at the final temperature to (nearly) consume all of the hydrogen present. The total amount of methane was-48 vol%, which corresponds to 1425ml methane. The methane production rate for this experiment was 63 ml/h. The pH was kept constant at 6.5.

Claims

1. A method for producing methane from carbon dioxide, hydrogen and one or more methanogens that are anaerobic archaea, comprising the steps of:

b) providing a cathode reaction vessel (12) containing a negative electrode (cathode), an aqueous growth substrate for electrolysis, one or more methanogens, carbon dioxide and hydrogen, wherein the cathode reaction vessel (12) and aqueous growth substrate for electrolysis are pressurized to a pressure of from 5 bar to 1000 bar using a pressurized fluid consisting of liquid carbon dioxide, or a pressurized fluid consisting of a mixture of liquid carbon dioxide and hydrogen;

c) connecting said anode reaction vessel and said cathode reaction vessel in a connection that allows electrons and/or ions to pass between the electrolytic media of said anode reaction vessel and said cathode reaction vessel;

-influencing hydrogen ionization in the cathode reaction vessel (12) to produce hydrogen gas and also to increase the pH of the aqueous growth substrate for electrolysis; and

influencing ionized oxygen in the anode reaction vessel (14) to form oxygen gas,

wherein electrolysis is performed intermittently to control the pH in the cathode reaction vessel (12).

2. The method of claim 1, wherein the cathode reaction vessel (12) and the anode reaction vessel (14) are operated at the same internal pressure.

3. A method according to claim 1, wherein the connection means is an electrolytic medium, a membrane is provided which allows the passage of electrons and optionally some ions, and the connection means is provided with a valve which is insulated from the electrolytic medium.

4. The method of claim 1, wherein the anode reaction vessel and the cathode reaction vessel are operated at different temperatures.

5. The method of claim 4, wherein the anode reaction vessel (14) is operated at ambient temperature and the cathode reaction vessel (12) is operated at a temperature that is optimal for the growth of the methanogen(s).

6. The method of claim 5, wherein the methanogen/s is/are hyperthermophilic, hyperpolarized, and nonpolar anaerobic archaea, and wherein the reaction in the cathode reaction vessel (12) is conducted at a temperature of 50 ℃ to 400 ℃.

7. The method of claim 6, wherein the reaction in the cathode reaction vessel (12) is carried out at a temperature of 80 ℃ to 200 ℃.

8. The method of claim 6, wherein the reaction in the cathode reaction vessel (12) is carried out at a temperature of 80 ℃ to 150 ℃.

9. The method of claim 5, wherein the methanogen/s is/are a psychrophilic/psychrophilic anaerobic archaea, and wherein the reaction in the cathode reaction vessel (12) is carried out at a temperature of-50 ℃ to 50 ℃.

10. The method of claim 9, wherein the reaction in the cathode reaction vessel (12) is carried out at a temperature of-5 ℃ to-20 ℃.

11. The method of claim 1, wherein the cathode reaction vessel (12) and the anode reaction vessel (14) are pressurized to a pressure of 5 bar to 500 bar.

12. The method of claim 11, wherein the cathode reaction vessel (12) and the anode reaction vessel (14) are pressurized to a pressure of 5 bar to 200 bar.

13. The method of claim 12, wherein the cathode reaction vessel (12) and the anode reaction vessel (14) are pressurized to a pressure of 10 bar to 150 bar.

14. The method of claim 13, wherein the cathode reaction vessel (12) and the anode reaction vessel (14) are pressurized to a pressure of 20 bar to 150 bar.

15. The method of claim 14, wherein the cathode reaction vessel (12) and the anode reaction vessel (14) are pressurized to a pressure of 40 bar to 150 bar.

16. The method of claim 1 wherein the cathode reaction vessel (12) is pressurized with a pressurized fluid consisting of a mixture of hydrogen and carbon dioxide.

17. The method of claim 16, wherein the hydrogen and carbon dioxide are present in a ratio of 4: 1 to 1: 4 are present in a molar ratio.

18. The method of claim 17, wherein the hydrogen and carbon dioxide are present in a ratio of 2: 1 to 1: 4 are present in a molar ratio.

19. The method of claim 18, wherein the hydrogen and carbon dioxide are present in a ratio of 1: 1 to 1: 4 are present in a molar ratio.

20. The method of claim 19, wherein the hydrogen and carbon dioxide are present in a ratio of 1: 2 to 1: 4 are present in a molar ratio.

21. The method of claim 1, wherein sufficient aqueous growth substrate for electrolysis is provided in the cathode reaction vessel (12) to provide a 1: 1 to 4: 1 volume ratio of aqueous growth substrate for electrolysis to headspace.

22. The method of claim 21, wherein the volumetric ratio of aqueous growth substrate for electrolysis to headspace is 2: 1 to 3: 1.

23. the method of claim 1, wherein the pH of the aqueous growth substrate for electrolysis is maintained in the range of 6 to 7.5.

24. The method of claim 23, wherein the pH of the aqueous growth substrate for electrolysis is maintained in the range of 6.5 to 7.

25. The method of claim 1, wherein the voltage applied across the positive and negative electrodes is from-0.2 v to-40 v.

26. The method of claim 25, wherein the voltage applied across the positive and negative electrodes is-2 v to-40 v.

27. The method of claim 26, wherein the voltage applied across the positive and negative electrodes is-10 v to-40 v.

28. The method of claim 27, wherein the voltage applied across the positive and negative electrodes is-20 v to-40 v.

29. The method of claim 28, wherein the voltage applied across the positive and negative electrodes is-25 v to-35 v.

30. The method of claim 1, wherein the direct current flowing across the positive electrode and the negative electrode is about 75 to 125 milliamperes.

31. An apparatus for producing methane from carbon dioxide, hydrogen and one or more methanogens that are anaerobic archaea, comprising:

a cathode reaction vessel (12) for containing carbon dioxide and water for electrolysis;

an anode reaction vessel (14) for containing water for electrolysis;

a negative electrode (cathode) capable of supporting anaerobic archaea methanogens located within the cathode reaction vessel (12);

a positive electrode (anode) located within the anode reaction vessel (14); and

connecting means for connecting the electrolysis water in the cathode reaction vessel (12) and the anode reaction vessel (14) so that a direct current can flow therebetween,

characterized in that the cathode reaction vessel (12) and the anode reaction vessel (14) are adapted to be pressurized to a pressure of 5 to 1000 bar, the cathode reaction vessel (12) is adapted to be pressurized with a pressurized fluid consisting of liquid carbon dioxide, or a pressurized fluid consisting of a mixture of liquid carbon dioxide and hydrogen, and the inner surfaces of the cathode reaction vessel (12) and the anode reaction vessel (14) are made of a non-conductive, non-corrosive material which insulates the electrolysis water from the rest of the apparatus except for the cathode and anode which are in contact with the electrolysis water within the cathode reaction vessel and the anode reaction vessel, and wherein an electrolysis reaction initiated by applying a direct current capable voltage across the anode and cathode serves to control the pH of the electrolysis water in the cathode reaction vessel,

wherein the connecting means is a conduit containing a liquid electrolyte.

32. The apparatus of claim 31, wherein the cathode reaction vessel (12) and the anode reaction vessel (14) are adapted to be pressurized to a pressure of 5 bar to 500 bar.

33. The apparatus of claim 32, wherein the cathode reaction vessel (12) and the anode reaction vessel (14) are adapted to be pressurized to a pressure of 5 bar to 200 bar.

34. The apparatus of claim 33, wherein the cathode reaction vessel (12) and the anode reaction vessel (14) are adapted to be pressurized to a pressure of 10 bar to 150 bar.

35. The apparatus of claim 34, wherein the cathode reaction vessel (12) and the anode reaction vessel (14) are adapted to be pressurized to a pressure of 20 bar to 150 bar.

36. The apparatus of claim 35, wherein the cathode reaction vessel (12) and the anode reaction vessel (14) are adapted to be pressurized to a pressure of 40 bar to 150 bar.

37. The apparatus of claim 31, wherein the conduit comprises a semi-permeable membrane that allows ions to pass between the electrolyzed water in the cathode reaction vessel (12) and the anode reaction vessel (14).

38. The apparatus of claim 31, wherein the conduit has a valve that is not in electrical contact with the electrolyte.

39. The apparatus of claim 31, wherein the negative electrode in the cathode reaction vessel (12) is in the form of a porous structure capable of supporting methanogen biofilm formation.

40. The apparatus of claim 39, wherein the negative electrode is a hollow microporous cylinder that is closed at one end and made of Pt amalgam or Pt, or other platinum group metal, titanium, or titanium plated with a platinum group metal.

41. The apparatus of claim 31, wherein the positive electrode in the anode reaction vessel (14) is made of Pt or a platinum group metal, or electroplated titanium.

42. Apparatus according to claim 31, comprising means for equalizing the pressure in the cathode reaction vessel (12) and anode reaction vessel (14).

43. Apparatus according to claim 42, wherein said pressure equalisation means is pressurised by the pressurised fluid used to pressurise said cathode reaction vessel (12) and also to pressurise said anode reaction vessel (14).

44. An apparatus according to claim 43, wherein the pressure equalizing means provides electrical insulation between the cathode reaction vessel (12) and anode reaction vessel (14).

45. The apparatus according to claim 43, wherein said pressure equalizing device comprises an electrically non-conductive tube having a piston therein, and an indicator for indicating the position of said piston within said tube.

46. The apparatus according to claim 31, comprising a thermal control device for heating or cooling the cathode reaction vessel (12).

47. The apparatus of claim 31, including an agitator within the cathode reaction vessel (12).

48. The apparatus of claim 31 wherein the conduit is located within a non-conductive heat resistant barrier between the cathode reaction vessel (12) and anode reaction vessel (14).